Avoid integer overflow when symmetrizing ellipse matrices

[FlorianPfaff]

Summary

• prevent integer overflow in tracking.ellipse_geometry.symmetrize
• scale each operand before adding it, so integer inputs are promoted before the potentially overflowing addition
• add a focused public-API regression test

Bug

The previous implementation evaluated matrix + matrix.T in the input integer dtype and only multiplied by 0.5 afterward. For example,

matrix = np.array([[120, 100], [80, 110]], dtype=np.int8)

should symmetrize to [[120, 90], [90, 110]], but the intermediate integer addition overflowed and produced [[-8, -38], [-38, -18]].

This affects public calls such as project_symmetric_covariance() when users provide integer array-like covariance input.

Fix

Use

0.5 * matrix + 0.5 * matrix.T

which preserves the mathematical result for floating-point inputs while promoting integer operands before addition.

Testing

Added tests/tracking/test_ellipse_geometry_integer_overflow.py, which passes an int8 covariance through project_symmetric_covariance() and checks both the correct numerical result and floating-point output dtype.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no	no	25.74s
✅ JSON	prettier	7	0	0	0	0.9s
✅ JSON	v8r	7		0	0	3.19s
✅ MARKDOWN	markdownlint	68	0	0	0	1.77s
✅ MARKDOWN	markdown-table-formatter	68	0	0	0	0.77s
✅ PYTHON	black	1866	87	0	0	88.88s
✅ PYTHON	isort	1866	139	0	0	2.73s
✅ REPOSITORY	betterleaks	yes		no	no	2.27s
✅ REPOSITORY	checkov	yes		no	no	52.28s
✅ REPOSITORY	gitleaks	yes		no	no	17.02s
✅ REPOSITORY	git_diff	yes		no	no	0.31s
✅ REPOSITORY	secretlint	yes		no	no	82.71s
✅ REPOSITORY	syft	yes		no	no	6.07s
✅ REPOSITORY	trivy-sbom	yes		no	no	5.66s
✅ REPOSITORY	trufflehog	yes		no	no	31.28s
✅ YAML	prettier	11	0	0	0	0.77s
✅ YAML	v8r	11		0	0	11.01s
✅ YAML	yamllint	11		0	0	0.53s

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